Analysis and Comparison of Modulation Schemes for a Laser Line Scan System at 10.6 Microns.

This paper provides background information to aid in the application of carbon dioxide lasers and optical heterodyne receivers to a proven target recognition and reconstruction technique. Specifically this paper weighs the feasibility of using various modulation schemes to provide the required range information. Analysis of the performance of various signal types indicate that signals of equal energy and equal bandwidth provide the same degree of estimation accuracy. Because of this selection of a modulation scheme is in this case influenced mainly by complexity of system operation associated with the modulation scheme. Sinusoidal AM requires the least system complexity of all the signals considered and is therefore a good choice for near-term implementation of the subject ranging technique. The object of this study is a proposed airborne ranging system which will scan an extended ground target providing target to aircraft range information with high angular resolution. The transmitter will scan a path transverse to the flight path and upon reaching the lateral limit, return to the original position. In this manner the transmitter covers a large path of the terrain as it flies. The receiver will measure and record the transmitter to target range at regular points along the lateral scan.